Factors affecting climate 

1. Latitude

2. Proximity to the sea

3. Nature of nearby ocean currents

4. Altitude 

5. Dominant winds

6. Cloud cover and aspect 

7. Differences in pressure systems

 

Latitude: At Equator, overhead sun is at a higher angle in the sky.

 

Proximity to the Sea

• Land heats up and cools down faster than water.

• Water is clear: sun's rays penetrate to great depth.

• Tides and currents cause heat to be distributed further. 

• Water has a moderating influence on climate

 

Ocean Currents

Ocean current: A body of water that moves in a specific direction, and will either be hot or cold.

 

Effect of warm ocean currents:

• Air is in close contact with the ocean, and gets warmer. 

• Warm air rises. 

• This contains a large amount of water vapour, as it is less dense. 

• Air is carried towards land and brings rainfall. 

 

Effect of cold ocean currents:

• Air is in close contact with the ocean, and gets colder. 

• This reduces the amount of evaporation from the ocean, as the air is denser. 

• The air is carried towards land and brings dry conditions.

• Therefore, the areas that lie close to these ocean currents may contain hot deserts.

 

Altitude

Air temperature decreases with increasing altitude

• Low altitudes: greater pressure; denser; warmer.

• High altitudes: lesser presser; less dense; thin air cannot retain heat.

 

Cloud Cover

Decreases insolation reaching/ leaving the surface by reflecting/ absorbing it. 

• When heat travels from the sun, it is not absorbed into the clouds, and reaches the land, making it very hot. 

• When the land loses its heat during the night, it is reflected back into the atmosphere, but is not retained in the clouds, thus making the land cooler. 

 

Pressure

Low pressure areas

• Caused by rising air 

• Produces rain: air rises, cools, condenses and forms clouds and rain. 

High pressure areas

• Caused by sinking air. 

• Rain formation is prevented.

 

Equatorial climate

• High temperature throughout the year/ low temperature range/ no seasons

• More cloud cover

• Average temperature: 30°C

• High rainfall throughout the year; around 2500 mm of annual rainfall

• High humidity

 

Factors influencing Equatorial climate

Latitude

• High temperatures due to low latitudes: sun is overhead/at a high angle/ sun’s rays are more concentrated

• No seasons because the sun is overhead throughout the year. 

 

Cloud cover

• Build-up of cumulus clouds

• Reduces heat loss at night, and so low diurnal range

 

Atmospheric pressure

• High rainfall due to low atmospheric pressure. 

• Large amounts of evaporation & transpiration due to rising air.

• Large amounts of condensation due to rising air.

• Saturation/convectional rainfall 

 

Explain why temperatures are high all year round in equatorial areas.

• They are close to the Equator/low latitudes

• Overhead sun/high angle (90 degrees)

• Concentrated rays/rays concentrated in small area/direct sunlight

• High/maximum insolation 

 

Explain why rainfall is always high in equatorial areas

• Heating by sun/high temperatures/direct sunlight

• Large amounts of evaporation/transpiration

• Ascending air/ convection

• Low pressure

• Cooling/condensation/saturation

• Convectional rainfall 

• Repeated each day

 

Processes which result in large amounts of cloud/ rainfall in equatorial areas - the typical daily weather pattern (convectional rainfall) in equatorial regions 

• Heating by sun/high temperatures/direct sunlight - The equatorial area heats up

• Evaporation/transpiration/ Evapotranspiration 

• Rising air/ Convection

• Cooling of air/water vapour

• Condensation; formation of clouds - cumulus/cumulonimbus clouds are formed

• Saturation/air mass cannot hold any more water

• Heavy rain falls 

• By sunset the sky is clear

• Repeated each day

 

Explain why there is little seasonal variation in climate in equatorial areas.

• Less difference between highest and lowest temperature

• They are close to the Equator/low latitudes

• Overhead sun/high angle (90 degrees)/ sun’s rays more concentrated

• High/maximum insolation

• There are no changes during the year in wind direction/angle of sun 

 

Hot Desert Climate

• High annual temperature range / Seasonal differences

• Lack of cloud cover; Large diurnal temperature range/High temperature during day & low temperatures at night

• Summer average around 30˚C–40˚C  (temperature can reach up to 50˚C

• Winter average around 15–20˚C  (temperature can go lower than 0˚C)

• Low rainfall; less than 250 mm of annual rainfall 

• Low humidity

 

Factors influencing hot desert climate

Latitude

• Close to the tropics

• High temperatures due to low latitudes: sun is overhead/at a high angle/ sun’s rays are more concentrated

• Has seasons due to the lower angle of the sun at different times of the year.

• High annual temperature range since angle of sun changes/tilt of the earth. 

• High pressure/sinking/descending air

 

Cloud cover

• Lack of cloud cover

• High diurnal range: Sun heats up area during day but heat escapes at night

 

Atmospheric pressure

• Low rainfall due to high atmospheric pressure. 

• Less evaporation & transpiration due to sinking/descending air

• Air heats as it descends/ no cooling 

• No cooling, so less condensation/ clouds do not form

• Precipitation is low/does not occur

 

Winds

• Trade winds/ winds blow from SE/ NE

• Prevailing winds blow across large areas of land

• Offshore winds /blows from a desert

• Dry winds/winds lose moisture before reaching desert/ does not pick up any moisture

 

Ocean Current

• Cold current

• Cold temperatures make air dense, and so is less likely to hold moisture; Rain falls at sea/air mass is dry when it reaches land. 

 

Rain shadow effect

• The air mass rises (on windward side) of mountain range

• Air expands

• Air mass cools

• Condensation of water vapour

• Saturation of air mass

• Precipitation on mountains

• Air descends

• Heating of air mass at leeward side

• No condensation takes place/no moisture in air/dry air

 

Distant from sea/ inland/ landlocked: So winds are dry by the time they reach them/winds have lost moisture. 

 

Formation of deserts near the Tropics - Due to Hadley Cells

• Air rises at the equator due to direct sunlight, condenses and brings convectional rainfall at the equator. 

• Some of the air near the Equator gets flung away due to Coriolis force, and sinks at around 23.5˚N and S of the Equator. 

• This sinking/descending air does not bring rainfall (when air moves downward, condensation does not take place). Thus, deserts are formed in these regions. 

• This circulation is called Hadley Cell: large-scale atmospheric convection cell in which air rises at equator and sinks at medium latitudes - 30˚N or S. 

 

Explain why temperature is high in a desert

• Low latitude

• On/close to the tropics 

• Sun is overhead/at a high angle/ sun’s rays are more concentrated

• Away from areas of sea/ocean/inland

 

Explain why deserts have high diurnal temperature range

• High daytime but cold night temperatures

• Lack of clouds allow high insolation during day

• Lack of clouds allows heat to escape at night

• Inland deserts - no moderating influence of sea

 

Explain why deserts do not receive much rainfall

• Lack of clouds 

• High atmospheric pressure

• Descending air

• No evaporation

• Far from water sources

• Wind direction over large areas of land/winds are dry by time reaches desert

• Rain shadow effect/wind or rain blocked by mountains

• Rain shadow

• Cold ocean currents

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Explain why there are usually more clouds in areas with an equatorial climate than in areas with a hot desert climate.

• Equatorial: low pressure at Equator vs. Deserts: high pressure

• Equatorial: rising air vs. Deserts: descending air

• Equatorial: more evaporation vs. Deserts: less evaporation

• Equatorial: more vegetation vs. Deserts: less vegetation

• Equatorial: more transpiration vs. Deserts: less transpiration

• Equatorial: high humidity vs. Deserts: less humidity

• Deserts: more distant from water bodies

• Winds to deserts are more likely to have blown over large areas of land. 

 

Tropical Rainforests 

Vegetation

Characteristics of rainforest vegetation 

• Evergreen

• Dense vegetation/trees close together

• Layers of vegetation

• Tall trees/emergents which grow taller towards the sunlight

• Straight trunks

• Trees have smooth barks to allow water to flow down to the roots easily

• Shallow roots

• Canopy of leaves/very little light penetrates

• Drip tip leaves/waxy leaves

• Lianas 

• Epiphytes/plants/fungi growing on trees

• Shrub layer – lower layer of small plants and shrubs

• Little undergrowth

 

Explain how the vegetation which grows in a tropical rainforest is influenced by the

climatic conditions.

• Evergreen due to all-year-round growing season

• Lots of vegetation/rapid growth due to constant/lots of rainfall

• Lots of vegetation/rapid growth due to high temperatures throughout the year 

• Emergents reach up for sunlight/fewer lower branches/straight trunks

• Buttress roots for stability/due to marshy ground

• Drip tip leaves to shed water, due to heavy rainfall

• Broad leaves to obtain more sunlight

• Shrubs/ground cover in clearings/where there is sunlight 

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Explain why trees in rainforests have buttress roots

• Because trees are so tall

• They support the tree: They prevent the tree being blown over/from falling over

• They increase surface area from which nutrients/water can be absorbed from soil

• They are better able to obtain nutrients from near the surface of the soil. 

 

Explain why some trees in the rainforest have drip tip leaves

• Because rainfall is heavy/constant. 

• To allow excess water from the leaves to run off quickly.

• To prevent the leaves from being broken off.

• To prevent fungus/bacteria growing on them. 

 

Rainforest nutrient cycle

• trees shed leaves all year round

• decaying vegetation decomposes rapidly, due to the presence of bacteria, fungi, etc. 

• nutrients enter the soil

• shallow roots take up the nutrients

• trees grow rapidly.

 

Rainforest Animals

• Arboreal species: Live in the canopy and rarely come to the ground. 

• Camouflage

• Evolved to look scarier than they really are

• Long, strong limbs for climbing

 

In tropical rainforests, why do some animals live in the canopy while others live in the ground cover?

• Some are able to climb/fly. 

• Some need shelter/protection/safety from predators. 

• Different food supplies available.  

• Different habitats/nesting areas.  

 

Explain why the tropical rainforest has a wide variety of insects and animals

• Rapid nutrient cycling

• Habitats for organisms/or example/provides shelter or shady areas

• Large supplies of food for insects/animals/birds/decomposers

• Many areas are still not exploited by people/little human disturbance

 

Describe ways in which vegetation, soil and wildlife depend on each other in a tropical rainforest.

• Wildlife eats plants (e.g. caterpillar eats booyong leaves)

• Birds/snakes eat small creatures (e.g. forest owl eats possum)

• Nutrients from dead animals are returned to soil; creatures’ faeces fertilise the soil

• Soil enables plants to grow; vegetation uses nutrients

• Population of species kept in check/in balance 

 

Layers of the rainforest

1. Emergents

2. (main) Canopy

3. Under canopy / understory

4. Shrub layer

5. Ground vegetation / forest floor 

 

Deforestation 

Importance of protecting rainforests for the natural environment and for locals 

• Protects the vegetation and stops the land becoming bare

• Habitat is retained

• Avoid disruption to food chain

• Reduces the threat of extinction/death of species/loss of biodiversity

• Reduces the threat of soil erosion/leaching/loss of fertility

• Maintains infiltration/less overland flow

• Flooding prevented

• Prevent river pollution/eutrophication. 

• No threat of air pollution/smoke from burning

• Ensures more food for locals

• Ensure locals have building materials

• Doesn’t destroy valuable medicines/undiscovered species

• Prevent introduction of Western diseases

• Tourism is retained

 

Causes of deforestation

• For economic growth to take place / to repay debt. 

• For logging/ export of wood/ firewood

• For pulpwood/paper making industries

• For mining 

• For agriculture/ commercial/cash crop production/ slash-and-burn

• Cattle ranching

• Road building 

• Building dams/generating HEP

• Weak legislation/corruption

• Exploitation of land by TNCs (transnational corporations)

• Population growth/urbanisation

• Industrialisation/ to build factories 

• Tourism / to build hotels

 

Impacts of deforestation 

On the local natural environment

• Release of carbon dioxide (as a result of burning)

• Trees are no longer available to convert CO2 to oxygen/less oxygen is produce

• Carbon dioxide traps heats

• Increases global warming/greenhouse effect

• Melting of ice caps/glaciers

• Rising sea levels

• Loss of habitat

• Impact on food chains

• Extinction of species

• Less nutrients are returned to the soil

• So they quickly become infertile 

• Drought 

• More rapid run of

• Flooding

• Leads to more soil erosion

• As there are no roots to stabilise soil

 

On locals

Benefits

• More land for agriculture 

• Timber for sale/source of timber

• Develop industry/roads/housing/building/construction/settlement

• Mining

• HEP/dams

• Remove dangerous animals

Problems

• Loss of wildlife/habitats/biodiversity

• Animals move into towns

• Soil erosion/loss of fertility/lower yields

• Landslides

• Flooding

• Lower rainfall

• Air pollution/smoke

• Loss of indigenous land

• Destroy natural beauty

 

Explain why soil erosion is likely to occur in an area that has been cleared of forests.

• Reduction of interception

• All the rainfall reaches the ground

• No roots to hold soil/ slow water down/absorb water

• Bare soil is exposed/no trees for shelter 

• Surface of soil becomes impermeable

• Large amount of surface runoff occur/less infiltration occurs

• Particles of soil are washed/carried away by the water

 

Explain how deforestation leads to flooding

• Reduction of interception

• All the rainfall reaches the ground

• No roots to hold soil/ slow water down/absorb water

• Bare soil is exposed/no trees for shelter 

• Surface of soil becomes impermeable

• Large amount of surface runoff occur/less infiltration occurs

• Soil erosion occurs/soil washed into rivers

• River silts up/capacity reduced

• Water is displaced 

 

Hot deserts 

Vegetation Adaptations 

Roots 

• Tap roots/ Long roots that reach down to water table/underground rocks

• Wide root systems/widely spaced to collect water from a larger area

 

Leaves

• Thorns/spikes to prevent evaporation

• Thorns/spikes to protect from predators

• No/ few/ small leaves to prevent transpiration/ water loss

• Hairy/ waxy leaves 

• Few stomata/pores/ sunken stomata

• Stomata closes at night to avoid transpiration

• Lose leaves during long dry spells

 

Stems/ barks

• Fleshy stems store water

• Tough/leathery/ridged bark

 

Seeds

• Seeds lie dormant and germinate in times of rainfall

 

Other features

• Low lying to protect against winds

• Wide distance apart to collect water from large area

• Light colours to reflect the sunlight

 

Desert Animals

Adaptations

• Can store water/ humps

• Eat succulent plants/get water from plant

• Thick outer covering to reduce moisture loss

• Their kidneys concentrate urine so that they excrete less water

• Large ears with many blood vessels to give off excess heat

• Shelter in underground burrows to avoid heat

• Only come out to hunt at night to avoid heat/ nocturnal 

• Large feet to stop sinking into sand

 

Ways in which natural vegetation, soil and wildlife are dependent on each other in a desert environment

• Vegetation needs the soil to grow/nutrients in the soil are used by the vegetation

• Animals/insects eat/get energy from/energy flows from plants

• Animals/predators eat/get energy from/energy flows from animals/insects

• Nutrients returned to soil from rotting vegetation/decaying fauna/animals excretion